Work Input vs. Work Output

Grade 10 · Physics

Semester 1 | Period 3 | Week 17

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Subject: Physics

Semester: 1

Period: 3

Week: 17

School Name:

Teacher’s Name:

Subject: Physics

Grade Level: Grade 10

Week & Period: Week 17, Period III

Date:

Sub-topic: Work Input vs. Work Output

Learning Objectives:
By the end of the lesson, learners should be able to:

  1. Define and distinguish between work input and work output.
  2. Relate the concepts of work input and output to efficiency.
  3. Perform calculations involving input, output, and efficiency.
  4. Understand energy loss and its effect on machines.

Instructional Materials:

  • Inclined planes and pulleys
  • Spring balances
  • Weights and load holders
  • Rulers and graph sheets
  • Efficiency charts

Anticipation (Warm-Up):
Ask:

  • “Have you ever used a machine that felt harder to use than expected?”
  • “Why might a machine not give you the same amount of work you put in?”

Building Knowledge:

  1. Work Input:
    • The total work done on a machine by the user
  2. Work Output:
    • The useful work done by the machine
  3. Efficiency:
    • A measure of how well a machine converts input work to output work

Solved Example:
A machine lifts a 60 N load through 2 m using 100 N effort over 4 m

  • Work Input = 100 × 4 = 400 J
  • Work Output = 60 × 2 = 120 J
  • Efficiency = (120 ÷ 400) × 100 = 30%

Experiment:
Title: Comparing work input and output using a pulley system
Materials: Pulley, spring balance, weights, meter rule
Procedure:

  1. Set up pulley with known load.
  2. Use spring balance to apply effort.
  3. Measure distances moved by effort and load.
  4. Calculate input and output work, then determine efficiency.

Activities:

  • Group calculations of input/output for various tools
  • Create bar charts comparing ideal and real output
  • Investigate causes of energy loss: friction, heat, deformation

Assessment:
Oral:

  1. Define work input and work output.
  2. What reduces the efficiency of machines?

Written:

  1. A man uses 80 J of work to move a 10 N object by 5 m. Calculate output and efficiency.
  2. If input is 300 J and output is 150 J, find the efficiency.

Homework:

  1. List five factors that cause energy loss in machines.
  2. Why can no machine be 100% efficient?

Expanded Notes:

  • In real machines, not all input becomes output due to energy losses.
  • Machines are rated by their efficiency, which determines usefulness.
  • Ideal machine: 100% efficient (not possible in reality).

Differentiation:

  • Use relatable examples (e.g. riding a bike uphill)
  • Provide scaffolds for formula-based problems
  • Create small group challenges to find most efficient machine

Teacher’s Reflection:

  • Did learners understand the concept of energy loss?
  • Were they able to apply input/output equations?
  • Which students need extra help calculating efficiency?